The electromagnet includes a coil system consisting of at least one circular cylindrical field coil and at least one correction coil concentric with the field coil. The coil system is enclosed in a ferromagnetic cylindrical shell whose influence on the homogeneity of the magnetic field is compensated by the particular dimensioning of the field and correction coils. The magnetic field is produced by the coil system in the interior space defined by it which space is accessible and suitable to accommodate an organic body for examination.
An electromagnet of the foregoing type is the object of the invention disclosed in U.S. patent application Ser. No. 386,981, now U.S. Pat. No. 4,490,675, issued Dec. 25, 1984. This earlier electromagnet utilizes a resistive coil system.